The AEMC Model 4620 is a digital ground resistance tester designed for field testing of grounding systems, soil resistivity, and bonding resistance.
Model 4620 (C-Cell Batteries): Powered by 8 standard disposable C-cell batteries.
Model 4630 (Rechargeable): Identical measurement specs and functions as the 4620, but powered by a built-in rechargeable NiMH battery pack with an integrated AC charger.
3-Point (3-Pole) Fall-of-Potential Testing: Standard ground rod and grounding grid resistance measurements.
4-Point (4-Pole) Soil Resistivity Testing: Measure soil resistivity ($\Omega\cdot\text{m}$) using the Wenner or Schlumberger methods before installing new grounding beds or cathodic protection systems.
2-Point (2-Pole) Continuity / Bonding Testing: Measure low-resistance connections between ground conductors, steel columns, and equipment frames.
| Parameter | Specification |
| Measurement Ranges | $0.00 \text{ to } 19.99\ \Omega$, $20.0 \text{ to } 199.9\ \Omega$, $200 \text{ to } 1999\ \Omega$ (Auto-ranging) |
| Resolution | $0.01\ \Omega$ on lowest range |
| Test Frequency | $128\text{ Hz}$ square wave (rejects stray power system currents) |
| Open-Circuit Voltage | $\le 42\text{ V Peak}$ |
| Power Source | Eight 1.5 V C-cell batteries (approx. 2000 15-second tests) |
| Enclosure | Heavy-duty, weatherproof field case (IP53 rated with lid open, IP65 with lid closed) |
| Noise Rejection | High noise immunity against stray ground currents and |
